Deep submergence equipment, such as remotely operated underwater vehicles (ROVs), is widely used in both civilian and military offshore endeavors. A typical submersible ROV is unoccupied, highly maneuverable, and operated by a person aboard a boat or ship. The ROV is linked to the boat or ship by a buoyant electromechanical cable, also called a tether, which carries electrical power and includes fiber optics for data communications. The cable needs to be neutrally buoyant at depth to allow good mobility and prevent the cable from getting entangled at the bottom of the sea.
The cable for a submersible ROV typically includes a cable floatation jacket. A thermoplastic elastomer with a specific gravity of about 0.88 has been used as a cable floatation jacket material. Because of the relatively high specific gravity of the elastomer, the diameter of the cable is quite large, inhibiting heat transfer and producing a high amount of drag. Another material that has been used for cable flotation jackets is a polyethylene foam. The polyethylene foam, however, is not elastic, absorbs water, and does not sustain large crushing pressures such as in a deep-sea environment. Glass microballoons have also been used in cable floatation jackets, however, the glass is very abrasive and can damage the cable drive system rollers. The glass material also does not improve the thermal conductivity of the cable floatation jacket.